Increasing attention is being given to monitoring the pressure of tires on a vehicle while the vehicle is in motion. A typical tire pressure monitor includes a plurality of transmitter circuits coupled to each of a plurality of tires on a vehicle, each transmitter circuit including a tire pressure sensor inserted into the tire and a radio frequency transmitter. The transmitter circuits sense tire pressure and generate radio frequency signals in the form of a message, the message including a tire identification number and the sensed tire pressure. The tire pressure monitor also includes a receiver circuit coupled to the vehicle for receiving the radio frequency signals. The receiver circuit processes the signals by, for example, displaying the tire pressures of each tire, providing warnings when the tire pressures are outside predetermined parameters, etc.
One challenge in tire pressure monitoring is identifying the location of the tires on the vehicle (e.g., left front, left rear, right rear, etc.). As tires are changed or rotated, the tire locations must be updated. In order to display the proper tire pressure to the driver for each tire, the locations of the tires must be known.
According to one prior system, signals coming via various reception antennas are processed not individually but rather together, and evaluated as to signal intensity for purposes of allocation to a specific wheel. The signals are summed, and the intensity of the summed signal is determined and compared to the intensity of a summed signal constituted by temporarily switching only Nxe2x88x921 reception antennas to the input of the receiver. The disconnected reception antenna is changed cyclically. According to the teachings of this system, the antenna whose deactivation results in the greatest intensity loss in the summed signal is normally that antenna which is located closest to the transmitting wheel electronics package, and thus receives the signal with the greatest field strength.
One drawback of this system is that some signals may be received with a higher signal strength at a reception antenna which is not closest to the position of the transmitting wheel, due to multipath, interference caused by spinning tires and surrounding objects, and other disturbances. This can lead to inaccurate results, which is disadvantageous in a system where it is very important to avoid providing misleading tire pressure data to the operator. Furthermore, this system requires multiple reception antennas, and, therefore, cannot be used with a tire pressure monitoring system having only one antenna.
Accordingly, what is needed is an accurate system and method for identifying tire position that does not require manual programming. Further, what is needed is a system and method usable on tire monitoring systems having one antenna or a plurality of antennas. Further still, what is needed is a system and method for passively identifying tire position that is more accurate and reliable than prior systems. Further yet, what is needed is a system that can detect tire position universally, i.e., without the need for a specialized transmission protocol. The teachings hereinbelow extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned needs.
According to one exemplary embodiment, a method of identifying the position of a tire on a vehicle includes receiving a plurality of wireless messages from a transmitter associated with the tire and determining the signal strengths of the received wireless messages. The method further includes providing a frequency distribution of the wireless messages based on the signal strengths and comparing the frequency distribution to a predetermined frequency distribution to determine the position of the tire on the vehicle.
According to another exemplary embodiment, a system for identifying the position of a tire on a vehicle based on wireless messages received from the tire includes a receiver circuit, a signal strength circuit, a memory, and a processing circuit. The receiver circuit is configured to receive the wireless messages. The signal strength circuit is configured to determine the signal strengths of the wireless messages. The memory is configured to store a predetermined frequency distribution. The processing circuit is configured to provide a frequency distribution of the wireless messages based on the signal strengths and to compare the frequency distribution to the predetermined frequency distribution to determine the position of the tire on the vehicle.
According to yet another exemplary embodiment, a system for determining the position of a tire on a vehicle includes a means for receiving a plurality of transmitted messages from a transmitter associated with the tire. The system further includes a means for determining the signal strength of the plurality of transmitted messages and a means for providing a pattern of the messages based on the signal strengths of the plurality of transmitted messages. The system further includes a means for determining the position of the tire on the vehicle based on the pattern of the messages and a stored pattern of signal strength values.